let uid = 0;
class Dep {
  constructor() {
    this.id = uid++;
    this.subs = [];
  }
}

Dep.target = null;
const targetStack = [];
export function pushTarget() {
  targetStack.push(target);
  Dep.target = target;
}
export function popTarget() {
  targetStack.pop();
  Dep.target = targetStack[targetStack.length - 1];
}
